The present invention broadly relates to an electrolyte composition and process for electrodepositing copper, and more particularly, to an electrolyte composition and process for the electrodeposition of copper from aqueous acidic copper plating baths, especially from copper sulfate and fluoroborate baths. More particularly, the present invention is directed to a novel additive system for producing bright, ductile, level copper deposits with good recess brightness on metal substrates, and particularly printed circuit boards, enabling usage of higher plating current densities in conventional electroplating equipment than heretofore possible.
A variety of aqueous acidic copper electroplating baths have heretofore been used or proposed for use incorporating various additive agents for electrodepositing bright, level and ductile copper deposits on various substrates. Typical of such prior art processes and electrolyte compositions are those described in U.S. Pat. Nos. 3,267,010; 3,328,273; 3,770,598; 4,110,176; 4,272,335 and 4,336,114 which, through mesne assignments, are assigned to the same assignee as the present invention.
While the electrolyte compositions and processes disclosed in the aforementioned United States patents provide for excellent bright, ductile and level copper deposits, problems are encountered when employing such electrolytes in conventional electrolplating apparatus when operating at relatively high cathode current densities, such as, for example, average current densities in excess of about 40 amperes per square foot (ASF) or higher. At such higher average cathode current densities to attain high speed plating of printed circuit boards, copper deposits are frequently obtained which are commercially unacceptable in accordance with the printed wiring board industry standards. It has been necessary, accordingly, to employ special electroplating equipment to enable the use of such higher average current densities in excess of about 40 ASF to achieve commercially acceptable deposits.
The present invention overcomes the problems associated with such prior art electrolyte compositions and processes by enabling high speed plating of copper at average current densities in excess of about 40 ASF in conventional equipment thereby achieving a high rate of electrodeposition of copper while at the same time attaining a copper deposit which meets the printed wiring circuit board industry standards.